I suppose it is somewhat forward looking that they went with the subcompact length rail (3.6" upper) and compact length grip (15-rounds) for the XCompact. It will fit both subcompact and compact upper, but I hope the rail is long enough to accommodate standard lights and lasers like the upcoming Surefire XH55. I use an X-series grip module (17-round) with a red-dot equipped compact upper and I would love to go down to a compact length grip module for CC and be able to pop on an XH55 for bedside duties.